Hot water (cph = 4188 J/kg∙K) enters a thin-walled double-pipe counterflow heat exchanger at 2.5 kg/s and 100°C. The overall heat transfer coefficient and the surface area are 1000 W/m2 ∙K and 21 m2 , respectively. For the cold stream, cold water (cpc = 4178 J/kg∙K) enters the heat exchanger at 5 kg/s and 20°C. (a) Determine the heat transfer rate for the heat exchanger (in W)